Ammonia-recovery process



Feb. 18, 1930. `1 BECKER 1,747,616

AMMONIA RECOVERY PROCES S Filed Aug. 2, 1922 4 Sheets-Sheet 1 y Feb. 18,1930. 1 BECKER 1,747,616

AMMONIA RECOVERY PROCESS Filed Aug. 2, 1922 4 Sheets-Sheet 2lll//I//l//l/l//l/ Feb. 18, 1930. J. BECKER 1,747,616

AMMONIA RECOVERY PROCESS y Filed Aug. 2, 1922 4 Sheets-Sheet 5 LLI/e71501 UWM Feb. 18, 1930. .1. BECKER AMMONIA RECOVERY PROCESS Filed Aug.2, 1922 4 sheets-sheet 4 Patented Feb. l, i930' PeTE1\1,1:forFICELA lJOSEPH 'IEJEICKIERy OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO THE'KOPPERS COM- ?PANY, OF PITTSBURGH,PENNSYLVANIA., A CORPORATION OFPENNSYLVANIA AMMONIA-RECOVERY PROCESS Application led August 2, 1922.Serial No. 579,147.

I This invention relates'to the recovery of ammonia from ammonia chargedgas such as coke oven gas .and has for its object the eficientproduction of ammonia from such gas,

'great economy'of heat or steam and with lsimplicity and directness 1nthe operation of the apparatus, and at the" same time eiectmg andmaintaining throughout the system av separation of ammonia liquors andcondensates containing fixed ammonia compounds and those containing(free ammonia compounds, and'separately recovering the ammonia from"such liquors and separately removlng or dlssipating the obnoxiousconstitu- "ents from the respective waste liquors and effecting separatedisposal of such waste liquorsij- Thefimproved process, whilemaintaining a high degree ofA etticiency in the recovery 'of the ammoniatromthev gas, reduces to about one-tenth in' volume the waste liquorcom- `monly"heretofore required to be evaporated 'fandfauthesame timevmakes effective vand useful disposal ofthe'rest ofthe waste liquor.

' T he'pr'obl'em 'of the` economical disposal of 'the' wasteiliquorfrom' a coke oven gas ammonia: recoveryvv plant has always been verydificult-ofI solution.` This. waste liquor contains `inj'additicnI`to'fthe 4calcium' 2 chloride resulting froniitlie lime treatment lof thefixed ammo- 'niafifi thestif'll other impurities such as phe- 'Iro'ls''andi cya lgenwhich prevent the discharge 'ofthe-'waste' liquor into anordinary aveste'Y inain,"becauseV ofthe contaminating:etfetfofsuchliquor v'upon the river water lin which fwould" vventua'llycommingle. In lordertfziiid"thi "aporation of this large volu'nie" ofliquor"atl great expense, it has been proposed; to pipetliefliquor tothe coke quenchirigstation and largely vvaporize it by quenchl Thisproposal, however, has not ccess4 `ecauseof the presenceof the liquorwhich cause s .itcentacts with the hot "'ly varded. The presentKorlz'eeping separate the in* here'covery of ammonia arged' gas andsepathe recovery of ammonia being effected with lt t at vthe quenching,ofi

' J'spo'slingvof it in such v manner that the fixed ammonia is removedfrom the gas separately from the free ammonia by a circulation of washliquor which is kept separate from the liquor involved in the recoveryof the free ammonia in all stages of the process, including the inaldisposal ot the separate waste liquors. Consequently the calcium bodieswill be present in only a part of the entire volume of liquor and thispro.- Y

portionof the liquor may be reduced to about one-tenth of the entirevolume employed in the by-product recovery plant, thereby reducing inlike degree the amount of waste liquor requiredto be speciallyevaporated, and eiecting an enormous saving of heat. Inasmuch as theremainder ofthe liquor, namely that part which is involved primarily inthe cooling of the gas and in the conden sation of free ammonia vapors,is distilled without lime treatment and is substantially free fromcalcium bodies, it may be pumped to the quenching station and theredisposed of in the quenching ofthe coke. The entire volume of liquor isthus effectively disposed 7 of with relatively great economy.v

Although herein described as specifically applied to the recovery ofammonia from coke oven gas, the invention may also be applied to thetreatment of other ammonia-charged gas, or gasthat is otherwise derivedfrom the carbo'nization of coal, and may also have such otherobjects andresults as are found to obtain in the processes hereinafter describedand claimed.

In the accompanying drawings:

Figure 1 is a conventional diagrani i1lus.4

another arrangement of apparatus for practicing its processes.

Referring now more particularly to Flg.

1 of the drawings:

There is indicated a-t 11 a battery of byproduct coke ovens, such asthose of the wellknown Koppel-s cross-regenerative type, from the cokingchambers of which the hot coke oven gas passes through the ascensionpipes 12 into the collecting main 13. Passing through the collectingmain 13, the coke oven gas is lirst discharged into the bottom of a hotliquor scrubber 14. This scrubber 14 is of the direct contact-type andmay be lled with hurdles to promote Ian intimate intel"- action betweenthe gas and the wash liquor, which is introduced into the top of thescrubber 14 fromthe flow pipe 15. In said. hot

liquor scrubber 14, the coke oven gas flows upwardly in countercurrentwith .the liquor flowing downwardly through said scrubber,

' .the gas discharging from ,the top of the scrubber through the gasdischarge pipe 16 and the lliquor discharging fromthe bottom ofthe'scrubb'er through a pipe '17 into the hot drain or settling tank 18.In the collecting main 13 andhot scrubber 14, the mass ofthe fixedammonia "content, which is 'ordinarily present in the form of an ammoniasalt such as ammonium chloride, is washed-outof the gas in the, form ofcondensate and passes with the wash liquor into the hot drain tank 18.

The liquid employed for. such scrubbing is preferably the aqueouscondensate of the gas from such scrubbing operation and the' liquidinitially employed in the tank 18 for such scrubbing is preferablyaqueous-condensate of the gas from the same ovens from which the gasbeing so treated is produced, or from other ovens, and vconsisting ofammonia liquor whichmay contain some tarr and possibly otherconstituents condensed out during the scrubbing operationl Although thetemperatureof'the gas drops slightly in the hot liquor scrubber 14, thegas passes out of said scrubber still containing the bulk of its freeammonia content which? is present in the gas in the form of vapor. Thewashing efected in the hot liquor scrubber 14 is not a'cooling step, butprimarily a washing operation, the gas in the scrubber 14` beingcooledjust suiciently to drop` below the dew .point of thecondensatecontaining the fixed ammoniafof the as, so that the ixed ammoniaiswashed out o the gas by the wash liquor, without any lsubstantialabsorption by the -wash liquor of the free ammonia vapors iny the gas.In the present illustrative "example the temperature of the gases-in thescrubber 14 may 'conveniently be around 70"y to 80 C. Inasmuchy as thewashliquor employed/in the scrubber 14 does not e`ect cooling of thegasto any 'great extent nor arly substantial absorption of the freeammonia, but fis em-A ployed primarily to scrubfout from the gas theresidue of fixed ammoniathat has not primarily to .remove the fixedammonia con` densate from the gas. y

The gas substantially freed of its fixed yammonia content but stillcarrying its free ammonia as vapor passes through the discharge pipe 16into the bottoni' of a direct cooler 19. The direct, cooler- 19 may beav gas and liquid vdirect contact apparatus similar to the hotliquorscrubber 14 but preferably of larger capacity, as indicated inFig. 1,. Passing upwardly through the direct cooler 19 the gas iscooled'in the ordinary way by cold liquor f which is discharged into thetop of the direct cooler 19 from rthe cold liquor pipe 20. The liquorcarrying part of the free ammonia of the gas discharges from the bottomof the direct cooler 19 through a discharge pipe 21 into the drain tank22, and the cooled gas passes out of the top of the direct cooler 19into 1the gas pipe 23' through which it passes to the exhauster 24. Asin the case of thetank 18, the liquorl initially employed in the tank 22for spraying the scrubber 19 is aqueous condensate of gas from the sameovens from which the gas being so treated by liquid from .tank

22 is produced, or from other ovens, and consisting of ammonia liquorwhichmay contain some tar and possibly other constituents con-.

densed out during the scrubbing operation. In the hot liquor scrubber 14a part of the tar content of the'gas is condensed and passes with thedischarged hot wash liquor into the A hot drain 18, Here, the tar isallowed to settle4 out in the bottom andmay be drained olf andcirculated tothe tar tank through the tar discharge pipe 25. The washliquor in the upper part of the tank is drawn oft' through a pipe 26 bythe pump 27 and is pumped through the hot wash liquor line-28 whichconnects with the valve controlled wash-liquor feedline 15 and with avalvec'ontrolled branch pipe 29 leading toV the collecting main 13. Partof the hot wash liquor, with lsome of the tar, is

in order to avoid: overheating of the main, and this spraying of themain at the same time eii'ects removal of the bulk of the fixed ammoniafrom the gas and leaves only a residue to be removed in the hot scrubber14. This liquor sprayed into the collecting main will ultimatelybe'restored to the fixed ammonia wash llquorpart of the systemcirculating.

through the hot liquor-Seru berv 14 and inthe 'y 120 -sprayed. into thegas in the collecting main 13,

tank 18. The remainder of the hot wash liquor flows through the pipe 28and .is partly circulated through a valve controlled branch to a coolingcoil 30 and partly through a valve controlled branch 31 to the top ofthe fixed leg 32 of an ammonia still 33. From the coil 30, which may beof the ordinary water cooled variety the hot wash liquor passes throughthe pipe V34 back to the hot drain tank'18. The cooling effected by thecoil 3() is just sufficient to prevent the temperature of the washliquor from rising above that required for washing out the fixed ammoniacondensate from the gas in the hot liquor scrubber 14.

From the gas main 16, the gas passes into the bottom of and up throughthe direct cooler 19, in which it is sprayed with cooling'v liquor fromthe pipe 20, such liquor with the condensate it gathers in the cooler19, being discharged through the pipe 21 into the tank 22. The coolingliquor and condensate discharged into the tank 22 through'tne pipe 21passes out of said tank through a pipe 3 5 and is pumped by the pump 35apartly through a valve controlled branch 36 leading to a" cooling coil37 and partly -through a valve controlled branch 38 leading to the topof the free leg 39 ofthe ammonia still 33. The liquor flowing throughthe coil 37 is cooled by water fiovvingfover the coil and at the outletof the coil discharges into the pipe 20 which rccirculates the coolingliquor back to the top of the direct cooler 19.

In the lower fixed leg 32 of the still the hot Wash liquor carrying thefixed ammoniaV is commingled with lime milk discharged into the stillthrough the pipe 40 to liberate the ammonia as vapor from the ammoniasalt. Steam is applied to the bottom of the still through the steam pipe41 and circulating in countercurrent with the liquor discharged into thetop of the fixed leg 32 and the upper free leg 39 drives oft the ammoniavapor from.

both liquors. The ammonia vapor from the lower fixed leg of the stillpasses upwardly into the upper free leg and there commingles with theammonia vapor recovered fromr the main body of the liquor. The entirebody of the ammonia vapor recovered in the still discharges through theammonia vapor pipe 42 and passes to the saturator 43.

The main body of the waste liquor, that isv volume of liquor employed isdischarged from the bottom of the free leg of the still through thedischarge pipe 45. This liquor, although also containing the obnoxiousphenols and cyanogen, contains substantially no calcium bodies and mayconveniently be disposed of by pumping it-.through the pump 81 andpiping 82, to the quenching station 83 and there employing it forquenching the coke, thereby dissipating the phenols and cyanogen by theheat of the coke.

From the exhauster 24 the gas 'passes through a pipe 46 into the bottomof a tar-extractor 47 in which the residue of the tar is removed fromthe gas. Passingy out of the top of the tar extractor the gasflowskthrough a pipe 48 into a reheater 49 in which the gas i's heatedand then delivered through a pipo 50 into 'a saturator 43. In thesaturator 43 the gasI` and ammonia vapors discharged through the ammoniavapor line 42, are subjected to an acid wash, for example sulphuricacid. for converting the ammonia vapors and the residue of ammonia inthe gas to ammonium sulphate, the gas being employed to eii'cct theprecipitation of the ammonia as ammonium sulphate'in the saturator 43.Discharging out of the saturator 43` holder for subsequent commercialuse. The ammonium sulphate preclpitated 1n the saturator 43 1s recoveredand dried.

iotav In the form of the invention. illustrate-d in" Fig. 2, the gasdischarged from the top of the direct cooler 19 passes through the pipe52vdi-l rectly into the bottom of the tar extractor 47 and from thetopof the tar extractor 47 through the pipe 53 directly into the bottom ofanother direct cooler 54 in which the cooled gas is employed for thepurpose of cooling part of the hot wash liquor discharged into the topof the direct cooler 54 through `the valve controlled branch line 282tin order to preserve an equilibrium in the temperature of the washliquor containing the fixed ammoniacompounds. From the bottom of thedirect cooler 54 the Wash liquor passes to the hot drain tank 18 throughthe pipe 34. lVith the above noted exception, the process illustrateddiagrammatically in Fig- 2 is the same as that previously described.

Figs. 3 and 4 both illustrate `processes in which an indirect cooler isemployedv for cooling the hot gas discharged from the top of the`hotliquor scrubber 14.V vIn the form of apparatus illustrated in Fig. 3they indirect cooler 55is of the vertical tube variety in which coolingwater is circulated through the i i Water tubes 56 from `a water inlet57 in the bottom of the coolen The water rises in the tubes on one sideof the cooler to a reservoir In 4 the indirect cooler of the horizontal'f Watertube variety isemployed. The cooler 62 is provided withhorizontal Water tubes 63 Which traverse a central gas :circulatingchamber. The gas enters the bottom of the cooler through ythe pipe 16and passing upwardly through the central chamber of the coolercirculates in contact with thehorizontal Water tubes 63 and finallyemerges through the top through the pipe 23. The Water enters achamber64 on one side of the cooler through an inlet pipe 65, passes throughthe lowertubes 63a to a chamber G6 on the other side,

` thence through the intermediate tubes 63" to a chamber 67 abovethechamber 64 and thence back through the upper tubes 63c to a cham? ber68 above chamber 6G. From chamber 68 the Water discharges through avdischarge pipe 69. The condensate from the bottom of the central gascirculating chamber discharges through a pipe 70 into the drain tank Ifdesired, in the form of the invention shown in 4, the tar which settlesout in the bottom of the hot drain tank 18 may be pumped through a tarline 71 by a pump 72 through a cooling coil 3 and thence conveyed by .atar line 74 to a spray 75, from which the tar is sprayed intothe gasrising in the cent-ral chamber of the indirect cooler 62. Thisfacilitates the removal of any tar and-napthalene from ythe gas and suchtar will flow with the condensate through the discharge pipe into thetank 22 and there settle out in the bottom.

IVhen indirect coolers are employed for cooling the gas, the liquorcontaining any free ammonia condensed in the cooling of the gas may begreatly reduced in volume thus requiring less liquor to be handled inthe free leg of the ammonia still. The volume of the liquor carrying thefixed ammonia absorbed from the gas in the main 13 and scrubber 14remains the same as previouslyv described. In the forms of the inventionillustrated in vFigs. 3 and 4 the cooler' 30 for maintaining theequilibrium of temperature of the fixed ammonia Wash liquor mayconveniently be interposed in the pipe line 28 between the pump 27- andthe branch line. leading to the top of the hot liquor scrubber 14.

In all forms of the invention it is preferable to provide a valvecontrolled over, flou pipe 76 leading from the top of the drain tank 22and adapted to discharge in the top of the hot drain tank 18. Thispermits the optional discharge of controlled quantities of the .liquorfrom the free am- `monia circulation system to the fixed ammonia washliquor system, for example, in making up the fixed ammonia vWash liquorsystem after a discontinuance of the latter for any cause.

The ,separate circulation, distillation and discharge and disposition ofthe liquor that takes the/ fixed ammonia and of the liquor that takesfree Vammoniafrom the gas, provides an efficient, practical andeconomical method of recovering ammonia from the condensates anddisposing of the objectionable and the obnoxious constituentsvin theContact with wash liquor and thereby removing the fixed ammonia contentfrom the gas; then cooling the gas by bringing it into direct contactwith a separate circulation of cooling liquor; subjecting the hot washliquor and the cooling liquor to separate distillingl v oaerations andseparately discharging. the Waste liquor therefrom; removing the residue-of the tar from the gas; and conducting the gas and the still vaporsfrom both distilling 'operations t-o and through a saturation bath torecover the ammonia; substantially as specified. y

2. In a processfor the recovery of ammonia from ammonia charged gas, thecombination of steps that consists in: washing. hot? ammonia charged gasby passing/it in direct contact with wash liquor and thereby removingthe fixed ammonia content from the gas; then cooling the gas by bringingit into direct contact with a separate circulation of cooling liquor;subjecting the hot Wash liquor and the cooling liquor to separate dis.-tilling operations and separately discharging the waste liquortherefrom; removing the residue of the tar from the gas; and `conductingthe gas and the still vapors from both distilling operations to andthrough a saturation bath to recover the ammonia; substantially asspecified.

3. In a process nia from coke oven gas, the combination of steps thatconsists in: Washing the hot gas for the recovery ofammofrom the cokeovens by passing it in direct Contact with wash 'liquor and therebyremoving the fixed ammonia content fromthe gas;

Ythen cooling the gas anddischarging any ammonia condensate separatelyfrom the wash liquor; subjecting the hot Wash liquor and the condensateto separate distillingoperations and separately discharging the Wasteliquor therefrom; removing the resispecified.

due of the tar from the gas; andconducting the gas and distilled vaporsfrom both distilling operations to and through a saturation bath torecover the ammonia; substantially as specified. Y.

4. In a process for the recovery of ammonia from ammonia charged gas,the combination of steps that consists in: Washing hot ammonia chargedgas by passing it in direct contact with Wash liquor and therebyremoving the fixed ammonia content from the gas; then cooling the gasand discharging any ammonia condensate separately from the Wash liquor;subjecting the hot Wash liquor and the condensate to separate distillingoperations and separately discharging the ivaste liquor therefrom;removingthe residue of the tar from the gas; and conducting the gas andstill vapors from both distilling operations to and through a saturationbathy to recover the ammonia; substantially as 5. In a process for therecovery of ammoma from coke oven gas, ythe combination of steps thatconsists in: washing the hot gas from the coke ovens by passing it indirect Contact with wash liquor and thereby removing the fixed ammoniacontent from the gas; then cooling the gas by bringing it into Contactwith a separate circulation of cooling lic uor thereby recovering freeammonia; and su jecting the hot Wash liquor and the cooling liquor toseparate distilling operations for the recovery of ammonia andseparately dis- 1 charging the Waste liquor therefrom; substantially asspecified.

6. In a process for the recovery of ammonia from ammonia charged gas,the combination of stepsthat .consists in: Washing hot ammonia chargedgas by passing it in direct contact with Wash liquor and therebyremoving the fixed ammonia content from the gas; then cooling the gas bybringing it into direct contact'with a separate circulation of coolingliquor thereby recovering free ammonia; and' subjecting the hot Washliquor and the cooling liquor to separate distilling operations for therecovery of ammonia and separately discharging thef` Waste liquortherefrom; substantially as specified.

7. In a process for the recovery of ammonia from ammonia charged gas,the combination of steps that consists in: Washing hot ammonia`chargedgas by passing it in direct contact with wash liquor and therebyremoving the fixedammonia content from the gas; then cooling the gas anddischarging any ammonia condensate separately from the hot Wash liquor;and subjecting the hot Wash liquor and the condensate to separate distilling operations for the recovery of ammonia and separately dischargingthe Waste liquor therefrom; substantially as specified. i

8. In a process for the lrecovery of ammonia from coke oven gas, theimprovement ing the hot Wash liquor and the cooling liquor; separatelydischarging the Waste liquors from the separate distillations;evaporating the waste liquor from the hot Wash liquor distillation; andpurifying the waste liquor from the cooling liquor distillation byemploying it in the quenching of incandescent coke; substantially asspecified.

ment characterized by Washing hot ammonia charged gas from the gasier bypassing it in direct contact With Wash liquor and thereby removing thefixed ammonia from the gas, then cooling the gas by bringing it intodirect contact with a separate circulation of cooling liquor; recoveringthe ammonia by separately distilling the hot Wash liquor and the coolingliquor; separately discharging the Waste liquors from the separatedistillations; evaporating the Waste liquor from the hot Wash liquordistillation; and purifying the Waste liquor from the cooling liquordistillation by employing it in the quenching of incandescent coke;substantially as specified.

10. In a process for the recovery of ammonia from ammonia charged gas;the improvement characterized by Washing the hot ammonia charged gas bypassing it in direct contact with Wash liquor and thereby removing thefixed ammonia content from the gas, then cooling the gas and dischargingthe condensate separately from the hot Wash liquor; recovering theammonia by separately distilling the hot Wash liquor and the condensate;separately discharging the Waste liquors from the separatedistillations; evaporating the Waste liquor from the hotwash liquordistillation; and purifying the Waste liquor from the condensatedistillation by employing it in the quenching of incandescent coke;substantially as specified.

11. In the process of recovering ammonia from ammonia charged gas, thecombination of steps consisting in separately recovering the fixedammonia liquor and the free ammonia liquor in successive steps of hotWashing treatmentand cooling of the gas current, respectively;separately distilling the two ammonia liquors for the recovery ofammonia; and separately discharging the two respective Waste liquors forfurther disposition; substantially as specified;

12. In a process of recovering ammonia from ammonia-charged gas, thecombination of steps of separately recovering the fixed ammonia liquorand the free ammonia'liquor 80 9. In a process for the recovery ofvammonia from ammonia charged gas, the improve- .6 KJ v .1,747,616

Vin successive steps of hot Washing treatment and cooling-of the gascurrent, respectively; distilling the fixed ammonia liquor and returningthe ammonia vapor tothe gas current; separately disposing of the wasteliq# uor from such distillation; and lseparately treating the freeammonia liquor to recover therefrom its free ammonia and to dispose ofits residual Waste liquor apart from the afore- 10 said Waste liquorfrom the fixed ammonia liq-j uor distillation, substantially asspecified;

13. In a process of recovering ammonia from ammonia charged gascontaining xed ammonia and other condensable constituents,

the combination of steps comprising separately dissolving,y atavtemperature above the volatilization temperature of free ammonia,

- the xed ammonia of the gas in a part of aqueous condensate condensedfrom the gas,

subjecting the aqueous condensate to indirect cooling and recirculatingit in a cyclic manner for further dissolving of fixed ammo- 'nia andsubsequent cooling, withdrawing condensate from said circulation forfurther disposition, subjecting the so treated gas to further cooling tocondense and remove other condensable constituents from the 'gas anddisposing of condensatefrom said further cooli ing ofthe gas separatelyfrom the condensate from saidcirculation; Y Y

In testimony Whereof'l have hereunto set my hand.

. JOSEPH BECKER;

